Turbine disk



1953 A. A. LOMBARD ETAL 2,628,065

TURBINE DISK Original Filed 001' 2, 1947 2 SHEETSSHEET 1 2 29 "'hw m. M

Ill."

A. A. 404154 EN. n. M02167 0. A. 04 ms,

Feb. 10, 1953 A. A. LOMBARD ,ET AL 2,628,065

TURBINE DISK Original Filed Oct. 2, 1947 2 SHEETS-SHEET 2 4. 4. 100M460,19M N. 4402465 Patented Feb. 10, 1953 TURBINE DISK Adrian AlbertLombard, Allestree, Frederick William Walton Morley, Aston-on-Trent,Christopher Ainsworth Davis, Barrow-on-Soak, near Loughborough, andStanley Clarke Wilkinson, Colne, England, assignors to Rolls-RoyceLimited, Derby, England, a British company Original application October2, 1947, Serial No.

777,506. Divided and this application December 19, 1950, Serial No.201,644. In Great Britain October 2, 1946 3 Claims.

This application is divided out of our copending application serial No.777,506 filed October 2,

This invention relates to gas-turbines and more particularly toturbine-disc-assemblies of the kind in which the turbine-disc comprisestwo complementary parts spaced axially and supporting peripherally theturbine-blading therebetween. In such constructions it has been proposedto provide a space between two parts of the disc forming a passag forair cooling the disc and blades and/or their fixing.

In gas-turbine engines for aircraft-propulsion, to which the inventionis particularly though not exclusively applicable, it has been thepractice to manufacture turbine-discs from solid forgings, which inorder to accommodate for high centrifugal loading and to avoid vibrationor whip,

.have been of relatively thick section. In addition, owing to theelevated temperature at the blade-root cooling efliciency.

The nature of the invention will be appreciated by reference to thefollowing description of a preferred embodiment illustrated in theaccompanying drawings, in which:

Figure 1 is a local radial section through a I turbine disc,

Figure 2 is a partial end view of Figure 1 with parts broken away.

Referring to Figures 1 and 2, there is illustrated an axial flow turbineassembly comprising two slightly dished disc parts with the turbineblading mounted in a blade-supporting ring received between theperipheral portions of the discs.

The two disc parts II), II are generally similar to one another,decrease in thickness from their centres towards their peripheries toeconomise in material and are assembled with the concave faces together.The disc material may be a high tensile steel, such as that known underthe trademark Hykro, having the desired properties at the moderatetemperature at which it runs.

The disc part is provided with a mounting flange l2 at its outer side bymeans of which the disc can be secured to a turbine-rotor shaft.

Each disc is formed with an internal axial flange It at about the sameradius as the mounting flange l2, and the flanges l3 abut one another tospace the two disc parts In, I l the correct distance apart at theircentres. One of the flanges is arranged to fit, in the manner of aspigot, within the other so as to resist centrifugal and gyroscopicforces, and thermal loading tending to cause relative radialdisplacement between the disc-parts.

Each disc part is formed with a central hole to receive a sleeve [4 andthe two disc parts are clamped together at their centres between aflange IE on the sleeve I4 and a nut 16 on the sleeve. The sleeve I4 isopen at one end to the shaft and is closed at the other so that coolingair can pass from the shaft into the sleeve and then through openings llin the sleeve l4 and flanges l3 into the turbine disc.

Each disc part I0, H is formed with an internal shoulder l8 near itsperiphery and these shoulders face radially inwards so as to formsockets of large diameter. Immediately outside the shoulder I8 the discparts are formed with two sets of annular facings I9 between which theblade supporting ring 20 is located. The material of this ring may bethat known as G.18.b (manufacturer's specification or trade-mark),having the desired properties at the elevated temperature to which thering is subjected. The ring 20 is formed with-two outwardly facingshoulders 2| which constitute large diameter spigots fitting in thesockets formed by the shoulders IS. The disc parts are secured towardstheir peripheries against moving apart axially by counter-sunk boltswhich are arranged in a circle along the centre-line of the facings l9and are thus in a portion of the disc which is subject to a considerablyreduced centrifugal loading, the centrifugal loading due to the blades23 and blade supporting ring 20 being applied to the disc through theengaging shoulders I8, 2 I.

The peripheral portions of the disc parts 10, II beyond the facings[Bf-are shaped to provide between them a wide trough 24 and theblade-supporting ring 20 extends radially outwards beyond the trough,the part of the ring 20 beyond the trough 24 being widened to close thetrough. There is, however, a space inside the trough on either side ofthe blade-supporting ring 20.

The facings l9 are formed with a plurality of radial slots 25 extendingacross them and also with arcuate slots 26 joining pairs of slots 25.The shoulders 2| on the ring 20 are also formed with radial slots 21 toregister with the slots 25.

The cooling air can thus pass into the trough 24 through the passagesprovided by these slots and will adequately cool the periphery of thedisc parts III, II and the in'n'er'part of the blade-supporting ring 20.

The peripheral part of the ring is formed with shaped recesses 29 toreceive and retain the roots 28 of the blades 23, the roots beingconveniently provided with peripherally extending shoulders so that theyare of the fir-tree type which are mounted in the blade-carrying ring bybeing slid into itin an axial direction. Slots 30 are cut across thebottom of the recesses 29 so that cooling air can escape from one sideof the trough 24 underneath the roots 28 of the blades. In certain casesthe blades 23 may be hollow and part of the air will then pass upthrough the blades to cool them. Passages 31 are formed in the portionsof the ring 2 3 between the blade roots 28 to permit the escape.ofcooling air from the trough 24 and to assist in cooling the bladeroots.

Each of the disc parts Hi, It is provided with .an axial flange 32 onits inner surface at a short distance inwards from the blade supportingring 20 and these flanges abut one another when the discs are assembled.Slots 33 are formed in the flanges 32 to register and form passages forthe outward flow of cooling air. The flanges 32 interabut to determinethe spacing of the discs l6 flanges 35 provide inwardly facing shouldersa forming sockets to receive a ring 35 which acts as a spigot in each ofthem. The ring 35 is preferably formed from a material, having a highcoefllcient of expansion, such as aluminium, so that it will tend totighten in the sockets as the temperature rises. The ring 35 is formedwith slot 38 on each of its side faces to provide passages through whichcooling air can pass outwards and each slot 35 is made deeper at itsouter end in order to clear the flanges 34. This arrangement has theresult that the air will tend to flow outwardly along the inner faces ofthe discs W, H to the slots 36 and will escape from these slots towardsthe central plane of the turbine-disc-assembly so that the two streamsof air flowing on the opposite sides ofv the ring 35 will be directedtowards the central plane of the turbinedisc and towards one another toproduce turbulence. This turbulence reduces the tendency for aStratified air flow in which the air flowing over the parts of the discwill be hotter than that flowing up the central plane of the disc.

' The spigot-like couplings between the bladesupporting ring 29 and eachof the disc parts iii, ll, between the ring 35 and the disc parts it,

H, and between the axial flanges l3 serve to resistcentrifugahgyroscopic or thermal loading which tend to make the discparts move relatively to one another in a radial direction.

The clamp device at the centre of the turbine disc assembly provided bysleeve i i, flanges i5 and nut 15, avoids the use of a series of boltspassing through the disc parts, and localizes the bore through thecentre of the disc, thereby avoiding undue reduction in structuralstrength. Likewise, it will be appreciated that the provision of theflange l2 avoids the passage of bolts through the disc-parts in theirattachment to the turbine shaft.

The disc parts l0, vll being coned will tend to separate undercentrifugal force at full speed. The-bolts 22 are tightened up so thatthe axial load between the flanges on the disc parts and between thedisc parts and the ring 35 are greater than the maximum force tending toseparate the disc parts when running at maximum speed.

It will be appreciated that the construction of turbine disc abovedescribed is light in weight and yet is capable of withstanding the highstresses experienced when in use, is relatively simple to manufacture,and, by virtue of the method of blade-root fixing, has an improvedcooling efiiciency as regards the blade-root cool- Moreover, by locatingthe screws, bolts or rivets for securing the disc together outside theregion of the part of their peripheries subjected to high centrifugalstresses, the discs are not unduly weakened by the provision of theholes to receive the bolts, screws or rivets.

Furthermore, the construction of turbine disc of this invention enablesthe various parts of the disc to be manufactured from a material havingthe desired strength properties at the temperature at which it willoperate. Thus the dished discs may be formed from a material havingdesired strength properties at a temperature which is moderate ascompared with that at which the biading or the blade-supporting ringwill operate and the blading or blade-supporting ring will be made froma material having desired strength properties at a more elevatedtemperature.

We claim:

1. An axial flow turbine assembly, comprising in combination a firstdisc part having means for securing it to a hollow rotor shaft; a seconddisc part mounted coaxially with the first and axially spaced therefromto provide a hollow space therebetween; a duct leading to said space forthe supply of coolinggas; shoulder means on said disc parts adjacent theperipheries thereof and extending axially towards one another; anannular blade supporting ring mounted in said space and provided withaxially extending circumferential spigot means abutting the radiallyinward faces of said axially extending shoulder means on said discparts; axial flow turbine blading supported by said blade supportingring; securing members to secure said disc parts against axialseparation extending through the disc parts, and through said ring andlocated at a radius outside said spigot means; and passages in saidaxially extending shoulder means and said axially extendingcircumferential spigot means communicating between said space and theexterior of the disc assembly to permit the flow of cooling gas fromsaid space, such flow cooling the ring and peripheral portions of thediscs by direct contact therewith.

2. An axial flow turbine assembly, comprising in combination twocomplementary disc parts secured to each other and axially spaced toprovide a hollow space therebetween means for supplying cooling gas tosaid space; axial abutment means on said disc parts defining said axialspacing at an inner radius; shoulder means on said disc parts at aradius outside said abutment means and extending axially towards oneanother; an annular blade supporting ring provided with axiallyextending circumferential spigot means abutting the radial inward facesor" said axially extending shoulder means; axial flow turbine bladingsupported by said blade supporting ring; securing members to secure saiddiscs against axial separation extending through said disc parts anthrough said ring and located at a radius outside said spigot means;circumferential shoulder means on said disc parts extending axiallytowards each other into said space and located at radius between saidfirst mentioned shoulder means and said abutment means defining theaxial spacing of the disc parts at inner radius; a spacer ring in saidspace engaged in axial abutment by said disc parts and dimensioned toengage in radial outward abutment with said circumferential shoulders;passages formed in said ring to permit passage of cooling gas radiallyoutward through said ring; and passages in said first mentioned shouldermeans and said axially extending circumferential spigot meanscommunicating between said space and the exterior of the assembly topermit the flow of cooling gas from said space, such flow cooling thering and peripheral portions of the discs by direct contact therewith.

3. An axial flow turbine disc assembly, comprising in combination afirst disc part; a second disc part mounted coaxially with said firstdisc part, said first and second disc parts having coaxial bores; ahollow bolt member extending through said bores; a nut member engaged onsaid bolt member; spacing means axially nipped between said discs bysaid bolt and nut members and holding said discs apart to provide ahollow space therebetween radially outside said spacing means; acommunicating duct from said coaxial bores to said space, saidcommunicating duct passing through said bolt; shoulder mean on said discparts adjacent the peripheries thereof and extending axially towards oneanother; an annular blade supporting ring provided with axiallyextending circumferential spigot means abutting radially inward faces ofsaid axially extending shoulder means on said disc parts; axial flowturbine blading supported by said blade supporting ring; securingmembers to secure said disc parts against axial separation extendingthrough said disc parts and through said ring and located at a radiusoutside said spigot means; and passages in said axially extendingshoulder means and said axially extending circumferential spigot meanscommunicating between said space and the exterior of the disc assemblyto permit the how of cooling gas from said space, such flow cooling thering and peripheral portions of the discs by direct contact therewith.

ADRIAN ALBERT LOMBARD.

FREDERICK WILLIAM WALTON MORLEY.

CHRISTOPHER AINSWORTH DAVIS.

STANLEY CLARKE WILKINSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 841,503 Gelpke Jan. 15, 19071,959,220 Robinson May 15, 1934 2,401,826 Halford June 11, 1946 FOREIGNPATENTS Number Country Date 452,412 Great Britain 1936

